The present invention relates to new catalyst systems for ammoxidizing propylene to produce acrylonitrile and for carrying out other oxidation-type reactions such as the oxidation of unsaturated olefins to produce the corresponding aldehydes and acids and the oxydehydrogenation of various olefins to produce diolefins.
Catalytic ammoxidation of propylene to produce acrylonitrile is a well known process. Many different catalysts have been described in the literature as effective in this process. Normally, it is indicated that such catalysts are effective at temperatures between about 200.degree. and 600.degree. C. The reaction, however, is very temperature sensitive and as a practical matter, temperatures on the order of 380.degree. to 400.degree. C. are necessary to produce significant amounts of acrylonitrile.
Most ammoxidation catalysts are formulated so as to maximize the yields of acrylonitrile, i.e. the amount of acrylonitrile produced based on the amount of propylene fed. The ammoxidation of propylene is normally carried out in a single pass mode, i.e. without recycle, and consequently maximizing single pass yields produces the greatest amount of acrylonitrile based on the amount of reactant used. However, it is possible to carry out the ammoxidation reaction in a recycle mode wherein some or all of the gross reaction product or unreacted reactants are recycled. In this situation, catalysts having superior selectivities, i.e. the ability to catalyze the reaction of interest as opposed to undesired side reactions, are more attractive. Unfortunately, catalysts which are formulated so as to produce acrylonitrile in high yields exhibit less that optimum selectivities.
Accordingly, it is an object of the present invention to provide a new class of catalysts suited for use in the ammoxidation of propylene and its homolog isobutylene to acrylonitrile or methacrylonitrile which exhibits high selectivities to the desired product and are also capable of operating at lower temperatures than conventional.